Environmental and Physiologic Factors Influencing IVF Outcomes
Many factors affecting IVF success are completely out of the patient’s control such as age, genetics, egg quality, response to ovarian stimulation, and embryo implantation. There are however some important factors that have a significant influence on the prospects for success that are under the couples control. Stress, diet, weight, and lifestyle are all considered to be modifiable factors that may improve prospects for successful IVF.
There has always been the uncertainty concerning whether stress causes infertility, or rather that infertility causes stress, and it has been difficult to design a study that might answer this question. There is however some preliminary evidence suggesting that active participation in a program teaching mind/body intervention raises the pregnancy by 15% per treatment cycle.
The pre-conception association of diet and the likelihood of pregnancy have been studied using a point system. One point is designated for each of the following food groups and amounts, 2 pieces of fruit per day, greater than 200 grams of vegetables per day, 3 or more servings of meat per week, 1 or more servings of fish per week, whole wheat products, and the use of mono and poly-unsaturated oils. While one could argue that these criteria do not constitute the perfect diet, most would agree that the listed food groups and portions do constitute a “minimum” basic nutritional standard. When patients were not meeting these minimum criteria, then made modifications to their pre-conceptual diet, they were significantly more likely to become pregnant.
Concerning diet and semen quality, a recent study suggests that as the amount of dairy in a man’s increases, sperm count decreases.
We know that two-thirds of women of reproductive age are overweight or obese. The odds of live birth from IVF decrease with increasing degrees of obesity. Similarly, egg quality diminishes with progressive obesity. One study has demonstrated a four-fold increase of abnormal spindles and chromosome misalignment in oocytes from severely obese patients. When overweight or obese women achieved a short-term weight loss of as little as 6-7 pounds, there was a significant increase in the percentage of mature eggs obtained at the time of egg retrieval.
Studies done thus far looking at the effects of alcohol, drugs, and caffeine on IVF outcomes have shown only a weak association with an increased risk of infertility. It is well established that heavy alcohol consumption severely suppresses spermatogenesis. Cigarette smoking has been shown to disrupt the delicate egg spindle resulting impaired fertilization potential.
There is some evidence that chemicals exist in the environment that may interfere with the production, release, transport, metabolism, or elimination of natural hormones. One of these chemicals, biphenyl A has been shown to have detrimental effects on eggs and sperm at higher concentrations than usually found in the environment. Biphenyl A is a chemical that was used in the manufacture of clear plastics such as water and baby bottles and to line the inside of water pipes, but its use has been banned. While there is some concern about these chemicals, at this time human exposure data are scarce. More studies are needed to determine if there is a blood concentration of endocrine disrupting chemicals such as biphenyl A that is detrimental to IVF success.
In summary, the following steps may prove beneficial for infertile couples preparing to go through in-vitro fertilization treatment:
1) Any therapy that decreases stress may increase IVF success rates
2) A healthy diet may increase the likelihood of IVF success
3) Obesity is associated with lower fertilization and live birth rates and weight loss for overweight patients should be encouraged.
4) Patients should be strongly encouraged to stop smoking before they start IVF.